Effet de filtre à spin dans les jonctions métal ferromagnétique / semi-conducteur : transport et effets d'interface

Abstract : Spin dependent transport of hot electrons injected from vacuum into hybrid ferromagnetic layer/interface/semiconductor structures is studied. This 3-terminal configuration is analogous to a spin valve transistor in which the emitter is physically decoupled from the base and the collector. This original configuration allows one to study the spin polarized electron transport over a wide range of energies while still controlling their polarization.
Using ferromagnetic junctions Fe/oxide/GaAs designed in the laboratory, four operating regimes in the energy range 10 eV-3000 eV are observed. When increasing the injection energy, the gain of the transistor increases by 6 orders of magnitude, reaching value as high as 300 at 3000 eV, while the spin dependent transmitted current increases by 5 orders of magnitude reaching a maximum value around 1500 eV. The latter corresponds to 30 % of the incident current for a 100 % polarized electron beam. Finally, it is shown that the main transport properties can be modulated by changing the total thickness of the metallic base, or indeed the nature of the interface between the base and the collector.
The four transport regimes are analyzed using an original quantitative model that takes into account both the multiplication which occurs in the metallic base and in the semiconductor by impact ionization, and the transmission coefficient at the interface between the base and the collector. In particular, the model reproduces experimentally observed threshold energies, above which the transmission efficiency increases steeply. By changing experimentally the injection energy it is possible to increase the hot electron distribution width at the base/collector interface until 10 eV and thus to probe the interface profile. The increase of the distribution width is linked to the special dependence of the inelastic mean free path with energy.
These results and their interpretations pave the way for future research in the field of spintronics, and especially in the design of a novel solid-state spin valve transistor device that could combine high spin selectivity with high gain and low operating noise.
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Contributor : Driss Lamine <>
Submitted on : Wednesday, March 5, 2008 - 11:08:33 PM
Last modification on : Wednesday, March 27, 2019 - 4:18:02 PM
Long-term archiving on : Thursday, May 20, 2010 - 9:29:57 PM

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  • HAL Id : tel-00260976, version 1

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Driss Lamine. Effet de filtre à spin dans les jonctions métal ferromagnétique / semi-conducteur : transport et effets d'interface. Matière Condensée [cond-mat]. Ecole Polytechnique X, 2007. Français. ⟨tel-00260976⟩

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